Steam & Excursion > Fire UNDER coal grates and its threat.

With recent discussions about melted cast iron grates.

In an effort to expand knowledge, let me start with the basics of coal grates.

Coal grates are made of cast iron.  Cast iron contains no carbon/iron molecules.
And those iron-carbon compounds produce steels.

Oxy-Acetylene cutting torches 'burn' the carbon out of the steels when subjected
to the temperstures and excess oxygen that neatly cuts steel.

Cast iron does not contain carbon, so it only responds to cutting torches set at
high temperatures by melting.

Cast iron, because of its strength, makes ideal material for making grate bars.

A good locomotive coal fire is a layered affair, .... there are distinct temperature 
layers in about a 4"-thick fire bed.   The top layer is fresh, 'green' coal applied by the fireman.
the layer below that is already burning, and is burning the 'low'  temperature 'volatiles'...
gasses from the breaking-down carbon fuel.

Below that 'reduction' layer is the almost consumed carbon fuel, then the layer on the grates
is the ashes-layer.  The ashes layer is coldest, exposed to the cold air drawn into the firebox 
by the draft provided by the exhaust jet up the stack.   So, the temperatures that the grates
see are intended to always be cold....except maybe at initial fire-up with brand new fuel on the
grates, and not yet converted to coal ash.

The biggest risk to grate bars is live coals and fire under the grates...  Fire above
AND below the cast iron is super HOT, and can melt the iron....as seen in the photos 
related to the earlier discussion.  

So, when "cleaning" the fire at the end of the day, and preparing for the next day, 
any ashes in the ash pan need to totally removed and sent down to the ash-pit....
and the ash pan washed with cold water.  
Ashes in the pit should be preferably soaked with water.... to extinguish any
remaining embers.

Ideally, you want to keep a layer of dead ashes  on the grates to block the cold air winds
from cooling-off the boiler,  way-too-soon.

Well cared-for grates can last for decades...

Lesson: Always keep Live Fire out from under the iron grates, they should always be cold to the touch!

​W.



 



Edited 6 time(s). Last edit at 09/22/22 07:38 by wcamp1472.

Cast iron does not contain carbon

I'm confused.  I thought what comes out of a blast furnace is iron with lots of carbon.  Burn off most of the carbon by various means such as a basic oxygen furnace and we call it steel which is still iron with carbon but only in a certain range.  And if it was possible to remove ALL the carbon (and it might not be possible) we must go back to calling it iron because iron is an element.  One source says that cast iron is iron with 2% carbon.

 

I stand corrected ----- cast iron is different than steel in that cast iron has 2%, or more, 
of carbon, and may contain other traces of impurities.
Steel has under 2% carbon.

Thank you for for the correction...

​W.

filmteknik Wrote:
-------------------------------------------------------
  I thought what comes out of a
> blast furnace is iron with lots of carbon.  Burn
> off most of the carbon by various means such as a
> basic oxygen furnace and we call it steel which is

Good point, cast iron is 2-4% carbon content while blast furnace iron is around 4% carbon. Steels are generally .3-.6% carbon content depending on grade desired, so a BOF is needed to go from 4% down to around .4% from the BF. Doesn't sound like much reduction but in reality is a huge difference in the final product...

JG

I remember a retired engineer tell about an incident that occurred when he was firing during the tail end of Wabash steam. He said the grates were really bad on the particular loco and he told the engineer to take it easy for that reason. But stubborn Chuck Ferguson wouldn't have any of that as he was a "Hot Rodder" and loved to run fast and furious with his locos. Well, according to George, account of the bad grates, he had a hard time keeping the fire banked, and they ran low on steam. It was a "I told you so" moment.

I wonder if the grates were damaged reference the subject of this post?

Victor B.

Edit: Bill Ferguson was the engineer, not Chuck. Chuck was his brother. The man that told me the story is George Thomas. AFIK, George is still living. In retrospect, I think that George said the the fire actually got dumped.



Edited 6 time(s). Last edit at 09/23/22 10:43 by wabash2800.